ESAB LAW 400, Service Manual

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15 PULSE WELDING
Pulse welding can only be performed with the LAW 400/410 when used together
with wire feed unit MEK 4SP.
The LAW 400 must have circuit board AP1 with part no. 0486 480 880 to perform
pulse welding. And additional wires 064, 065 and 066 between connectors XS1 and
XS15.
There is only one voltage reference from the wire feed unit to the power source.
However, two different voltage reference signals are needed for pulsing: one for the
peak voltage (Utop) and one for the background voltage (Ub).
As Utop is always the same within the same synergy line, the wire feed unit sends
the peak voltage reference signal to the power unit immediately when a pulsed
synergy line has been selected, and it is then stored in memory in the power unit.
The wire feed unit then transmits Ub continuously to the power unit as long as
welding continues on the same synergy line.
Utop is transmitted from the feed unit for about 300 ms, when a pulsed synergy line
is selected.
The pulse frequency is 42.8 Hz and controlled by the power source.
Input H4 pulsing signal
The pulsing signal, H4, tells the power unit that pulsing has been selected.
H4 goes low (0 VB) when pulsing has been selected.
Input H5 pulse voltage signal
H5 goes low (0 VB) for about 300 ms when the Utop voltage reference signal is
transmitted from the feed unit.
Input H6 pulse programming signal
H6 goes low (0 VB) when custom synergy lines are being constructed in the pulse
mode. See the programming description in the MEK 4SP service manual.